1. Field of the Invention
The present invention relates to an inductor and an electronic power supply using it. More specifically, the present invention relates to an inductor used in a smoothing circuit of a power supply circuit for large scale integrated circuits (LSIs) mounted on a printed wiring board, and a power supply circuit including the same.
2. Related Art
Recently, in semiconductor devices such as an LSI used in an electronic device, the driving voltage has been decreased to a very low value, about 1 volt, in order to achieve high performance and low electric power consumption. In order to provide such an LSI load with a driving electric power, it is necessary to provide electric power obtained by rectifying an alternating current to a direct current and decreasing the voltage in several stages. For such an application, A DC-DC converter with excellent conversion efficiency is generally used. In this case, noises during output must be suppressed using a smoothing circuit.
The smoothing circuit mainly includes two types of elements, namely, inductors and capacitors for which surface-mount devices are mainly used. The mounting of such surface-mount devices on a printed wiring board requires a certain area for mounting.
According to an inductor disclosed in FIGS. 1 and 2 in Japanese Patent Laid-open Publication No. HEI 1-312885 “Circuit Board with an Inductor embedded therein”, (publication Date: Dec. 18, 1989), a cylindrical ferrite body 20 is fitted in a through-hole 18, and a conductor 24 is inserted into a through-hole 22 of the cylindrical ferrite body 20.
However, microscopically, unlike an “inductor including a conductor and a magnetic body that is in contact with the conductor with no gap therebetween” described below, this structure includes an gap between the conductor and the magnetic body, and thus a high inductance cannot be obtained.